Barberpole Effect
This animation simulates a set of black and white stripes moving rightwards behind a black mask with four holes. Look at the leftmost hole and compare it with the bottom center hole. These are instances of the "barberpole" effect (Wallach,1935/1996). The perceived direction of motion is the predominant direction of the stripe terminators, following the longest side of the hole. In the rightmost hole, the sides are first horizontal, then vertical, then turn horizontal again. Accordingly, the stripes appear to go right, turn downwards, and then turn right again. In a circular hole, the terminators do not have a predominant direction and the stripes appear to move perpendicularly to their orientation. The barberpole effect suggests that contour terminators play an important role in determining the perceived motion of an object.


created by Fauzia Mosca and Nicola Bruno